Crystalline molecular sieves have a three-dimensional, four-connected framework structure of corner-sharing [TO4] tetrahedral units, where T is any tetrahedrally coordinated cation. Among the known forms of molecular sieves are aluminosilicates, which contain a three-dimensional microporous crystal framework structure of [SiO4] and [AlO4] corner-sharing tetrahedral units; aluminophosphates, in which the framework structure is composed of [AlO4] and [PO4] corner-sharing tetrahedral units; and metalloaluminophosphates, in which the framework structure is composed of [MO4], [AlO4] and [PO4] corner-sharing tetrahedral units. The metal (M) is usually selected from the group consisting of silicon, magnesium, zinc, iron, cobalt, nickel, manganese, chromium, and combinations thereof.
Molecular sieves have been classified by the Structure Commission of the International Zeolite Association (IZA) according to the rules of the IUPAC Commission on Zeolite Nomenclature. According to this classification, framework-type zeolite and zeolite-type molecular sieves, for which a structure has been established, are assigned a three-letter code and are described in the “Atlas of Zeolite Framework Types,” Sixth Revised Edition, Elsevier, 2007.
One known molecular sieve for which a structure has been established is the material designated as DFO, which is a molecular sieve having two parallel channels of circular pore apertures of about 6.1 Å and 7.5 Å respectively with interconnecting 8- and 10-ring channels. The known member of the DFO framework type is DAF-1, a magnesium-substituted aluminophosphate.
P. A. Wright et al. (J. Chem. Soc., Chem. Commun. 1993, 633-35) disclose molecular sieve DAF-1 and its synthesis under hydrothermal conditions using a decamethonium cation as a structure directing agent.
It has now been found that crystalline zinc (silico)aluminophosphate molecular sieves isostructural with the DFO framework type can be synthesized using a 1,3-dialkylimidazolium-based ionic liquid as both the solvent and the structure directing agent.